Crystal samarium

Hydrochloric acid Succinic acid neutralizer, preboiler system Methoxypropylamine neutralizer, urea-formaldehyde resins Ammonium biborate neutron absorber Boron carbide Samarium oxide neutron absorber, laser crystals Samarium... 

Samarium has a bright silver luster and is reasonably stable in air. Three crystal modifications of the metal exist, with transformations at 734 and 922oC. The metal ignites in air at about ISOoC. The sulfide has excellent high-temperature stability and good thermoelectric efficiencies up to llOOoC. 

Materials. Beside inorganic materials (eg, barium chloride/fluoride crystals, doped with 0.05% samarium), transparent thermoplasts are preferred for the PHB technique, eg, poly (methyl methacrylate) (PMAIA), polycarbonate, and polybutyral doped with small amounts of suitable organic dyes, organic pigments like phthalocyanines, 9-arninoacridine, 1,4-dihydroxyanthraquinone [81-64-1] (quinizarin) (1), and 2,3-dihydroporphyrin (chlorin) (2). 

MIR), requires the introduction of new x-ray scatterers into the unit cell of the crystal. These additions should be heavy atoms (so that they make a significant contribution to the diffraction pattern) there should not be too many of them (so that their positions can be located) and they should not change the structure of the molecule or of the crystal cell—in other words, the crystals should be isomorphous. In practice, isomorphous replacement is usually done by diffusing different heavy-metal complexes into the channels of preformed protein crystals. With luck the protein molecules expose side chains in these solvent channels, such as SH groups, that are able to bind heavy metals. It is also possible to replace endogenous light metals in metal-loproteins with heavier ones, e.g., zinc by mercury or calcium by samarium. 

Samarium, tris(triphenylphosphine oxide)bis-(diethyldithiophosphato)-structure, 1,78 Samarium complexes dipositive oxidation state hydrated ions, 3, 1109 Samarium(III) complexes salicylic acid crystal structure, 2, 481 Sampsonite, 3, 265... 

These new silyl complexes are monomeric in benzene solution, but are dimeric in the solid state. The crystal structure of the samarium analogue (Figure 1) shows that dimers form via intermolecular Sm-CH3-Si interactions. The Sm-Si distance, 3.052 (8) A, is to our knowledge the longest metal-silicon distance known. As with other complexes that display Ln-CH3-Si interactions in the solid state, evidence for these interactions in solution is not observed in NMR spectra. The [H NMR chemical shifts for the neodymium... 

The crystal structure of the 1 2 adduct 145 obtained by the reaction of [Cp SmH]2 with MMA was determined by X-ray analysis. One of the two monomer units is in the O-enolate form and the other unit coordinates to the samarium atom by the carbonyl group. A comparison between 145 and the... 

Fig. 9. The crystal and molecular structure of tids(indenyl)samarium(III), from Ref. (56)...

The compounds Ln(C5H5)2Cl also have been made only with the lanthanides above samarium (772). These compounds are stable in the absence of air and moisture, sublime near 200 °C, are insoluble in non-polar solvents, and exhibit room temperature magnetic moments near the free ion values (772, 113). The chloride ion may be replaced by a variety of anions including methoxide, phenoxide, amide and carboxylate. Some of these derivatives are considerably more air-stable than the chloride — the phenoxide is reported to be stable for days in dry air. Despite their apparent stability, little is known about the physical properties of these materials. The methyl-substituted cyclopentadiene complexes are much more soluble in non-polar solvents than the unsubstituted species. Ebulliometric measurements on the bis(methylcyclopentadienyl)lanthanide(III) chlorides indicated the complexes are dimeric in non-coordinating solvents (772). A structmre analysis of the ytterbium member of this series has been completed (714). The crystal and molecular parameters of this and related complexes are compared in Table 5. 

Samarium salts are used in optical glass, capacitors, thermoionic generating devices, and in sensitizers of phosphors. The metal is doped with calcium fluoride crystals for use in lasers. It also is used along with other rare earths for carbon-arc lighting. Its alloys are used in permanent magnets. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

Samarium sesquioxide dissolves in mineral acids, forming salts upon evaporation and crystallization ... 

Samarium-neodymium evolution diagram for lunar mare basalt 75075. Data points for the total rock, plagiodase, ilmenite, and pyroxene form a precise linear array, the slope of which gives a crystallization age of 3.70 0.07 Ga for this rock (7= 6.54 x 10 12 yr 1). The insert shows the deviations from the best-fit line in parts in 104. After Lugmair et al. (1975a). 

A number of X-ray crystal determinations have made the principles of lanthanide cryptate structural chemistry fairly clear. In [La(N03)2(2,2,2-cryptate)][La(N03)6] (Figure 8), the La3+ ion is 12-coordinated with two bidentate nitrate ions coordinating in two of the three spaces between the cryptate chains the third space is thus too compressed to be occupied also.508 [Sm(N03)(2,2,2-cryptate)][Sm(N03)5(H20)] shows only one such space occupied511 and the structure of [Eu(C104)2,2,2-cryptate](C104)2MeCN is similar to the samarium cryptate.512,513 Intemuclear distances in these complexes are shown in Table 10. 

Although all the lanthanides are stable in the solid state as M2+ ions doped into CaF2 crystals, only in the cases of europium, ytterbium and samarium is there any real coordination chemistry, and that is very limited. There is a small but developing organometallic chemistry of the lower oxidation states,641 but that is not within the scope of the present review. Much of the chemistry of the dipositive state depends on solvated species642 and it is convenient to begin with these. 

Arsenate. — The arsenates of the rare earths crystallize [263] in two structural types, the huttonite and the zircon. The structural change from huttonite (La—Nd) to zircon (Sm—Lu) occurs at samarium. The lattice parameters of EuAsCU are a = 7.167 and c — 6.374 A. The rare earth arsenates can be prepared by reacting the nitrates with (NEU HAsCU, and heating the product to 700° C. 

SAMARIUM. [CAS 7440-19-9]. Chemical element symbol Sm, at. no. 62, at. wt. 150.35, fifth in the Lanthanide Series in the periodic table, mp 1,073°C, bp l,79l°C, density 7.520 g/cm3 (20 C). Elemental samarium has a rhombohedral crystal structure at 25DC. The pure metallic samarium is silver-gray in color, retaining a luster in dry air, but only moderately stable in moist air, with formation of an adherent oxide. When pure, the metal is soft and malleable, but must be worked and fabricated under an inert gas atmosphere. Finely divided samarium as well as chips from working are... 

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